using an object's key as a variable in JavaScript

Question

using an object's key as a variable in JavaScript

Is it possible to reference an object's key as a variable and then modify its value? I am experimenting with the following:

const obj = {
  x: {
    y: {
      z: 'test'
    }
  }
}

const func = () => {
  let root = obj['x'];
  root = 'test 2';
}

func();

console.log(obj);

I am currently working on a recursive function to change root to something like obj['x']['y'].

javascript

Answer 1

Answer №1

If I am interpreting your inquiry correctly, the response is most likely "not without resorting to some unconventional methods." It appears that you are inquiring about this scenario:

const obj = {
  x: {
    y: {
      z: 'test'
    }
  }
}

You wish to store obj.x (or alternatively, obj['x']) into a variable such that modifying that variable will result in a change to the x field of object

obj</code. This task cannot be accomplished as desired. Once you establish the connection with:</p>

<pre><code>let root = obj.x

Any subsequent reassignment to root will not affect

obj</code at all; this means that <code>root

acts independently from

obj</code. Visualizing it might help clarify this concept. Nevertheless, <code>root

essentially serves as a reference to obj.x, so if you were to execute:

root.y = 'test 2'

This action indeed alters obj.x.y.

However, it is important to note that you are unable to assign obj.x to a variable and then leverage that variable to modify the x field within

obj</code. Modifications can only be made to fields WITHIN <code>obj.x

. In contrast to languages like C++, JavaScript lacks the capability to create aliases or manipulate lvalues.

If your intention is truly to update the x property of

obj</code, you should solely store the string <code>x

in a variable like so:

root = 'x'

Then you could proceed with the following:

obj[root] = 'a new value for obj.x'

This operation will bring about changes to obj.x. However, bear in mind that evaluating obj.x first and using that result to modify

obj.x</code is not a feasible approach. Well, unless you delve into complicated tactics like this:</p>

<pre><code>root = 'obj.x';
eval(`${root} = 'a new value for obj.x';`);

Steer clear of such convoluted methods.

Moreover, if obj itself was also a variable, you could carry out the following procedure:

receiver = obj;
prop = 'x';
Reflect.set(receiver, prop, 'the new value')

Hopefully, my interpretation aligns with your objectives. Regardless, perhaps this explanation may spark some ideas.

Answer 2

If I am interpreting your inquiry correctly, the response is most likely "not without resorting to some unconventional methods." It appears that you are inquiring about this scenario:

const obj = {
  x: {
    y: {
      z: 'test'
    }
  }
}

You wish to store obj.x (or alternatively, obj['x']) into a variable such that modifying that variable will result in a change to the x field of object

obj</code. This task cannot be accomplished as desired. Once you establish the connection with:</p>

<pre><code>let root = obj.x

Any subsequent reassignment to root will not affect

obj</code at all; this means that <code>root

acts independently from

obj</code. Visualizing it might help clarify this concept. Nevertheless, <code>root

essentially serves as a reference to obj.x, so if you were to execute:

root.y = 'test 2'

This action indeed alters obj.x.y.

However, it is important to note that you are unable to assign obj.x to a variable and then leverage that variable to modify the x field within

obj</code. Modifications can only be made to fields WITHIN <code>obj.x

. In contrast to languages like C++, JavaScript lacks the capability to create aliases or manipulate lvalues.

If your intention is truly to update the x property of

obj</code, you should solely store the string <code>x

in a variable like so:

root = 'x'

Then you could proceed with the following:

obj[root] = 'a new value for obj.x'

This operation will bring about changes to obj.x. However, bear in mind that evaluating obj.x first and using that result to modify

obj.x</code is not a feasible approach. Well, unless you delve into complicated tactics like this:</p>

<pre><code>root = 'obj.x';
eval(`${root} = 'a new value for obj.x';`);

Steer clear of such convoluted methods.

Moreover, if obj itself was also a variable, you could carry out the following procedure:

receiver = obj;
prop = 'x';
Reflect.set(receiver, prop, 'the new value')

Hopefully, my interpretation aligns with your objectives. Regardless, perhaps this explanation may spark some ideas.

Answer 3

Answer №2

function updateRoot() {
  let rootValue = obj['x'];
  rootValue = 'test 2';
}

This function changes the value of the variable rootValue without affecting the object. To update the object directly, use the following code:

obj['x'] = 'test 2'

const obj = {
  x: {
    y: {
      z: 'test'
    }
  }
}

function updateObject() {
  obj['x'] = 'test 2';
}

updateObject();

console.log(obj);

Alternatively, you can modify a specific value within the object using the rootValue variable:

const obj = {
  x: {
    y: {
      z: 'test'
    }
  }
}

function updateFieldValue() {
  let rootValue = obj['x'];
  rootValue['y'] = 'test 3';
}

updateFieldValue();

console.log(obj);

Answer 4

function updateRoot() {
  let rootValue = obj['x'];
  rootValue = 'test 2';
}

This function changes the value of the variable rootValue without affecting the object. To update the object directly, use the following code:

obj['x'] = 'test 2'

const obj = {
  x: {
    y: {
      z: 'test'
    }
  }
}

function updateObject() {
  obj['x'] = 'test 2';
}

updateObject();

console.log(obj);

Alternatively, you can modify a specific value within the object using the rootValue variable:

const obj = {
  x: {
    y: {
      z: 'test'
    }
  }
}

function updateFieldValue() {
  let rootValue = obj['x'];
  rootValue['y'] = 'test 3';
}

updateFieldValue();

console.log(obj);

Answer 5

Answer №3

Simply transfer the data

const newObj = { a: { b: { c: 'example' } } }

remove Object.assign(newObj, {freshKey: newObj.staleKey }).staleKey;

Answer 6

Simply transfer the data

const newObj = { a: { b: { c: 'example' } } }

remove Object.assign(newObj, {freshKey: newObj.staleKey }).staleKey;

using an object's key as a variable in JavaScript

Answer №1

Answer №2

Answer №3

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